Arthroscopically Repaired Bankart Lesions and the Effect of Two Different Arm Positions on Immediate Postoperative Evaluation With Magnetic Resonance Arthrography

Purpose: To evaluate and describe the findings of immediate postoperative magnetic resonance (MR) arthrography of repaired capsulolabral buttress using 2 different arm positions (internal rotation and external rotation) for patients who have undergone arthroscopic Bankart repair. Type of Study: Case series. Methods: Arthroscopically repaired Bankart lesions in 22 nonconsecutive patients were examined with axial T2-weighted MR arthrography. We studied each of the 22 shoulders on the day of surgery for each patient. We measured 3 parameters (height, slope, and medial overhang) on the axial image at the anteroinferior portion of the glenoid (near the most inferior anchor) while placing each patient's arm into 2 different positions. The first involved internal rotation and the second, external rotation of the shoulder with the arm held at the side of the trunk and the elbow at 90° flexion. The mean internal rotation of the arm was 30° (range, 14° to 45°) and the mean external rotation was 19° (range, 2° to 44°). Results: The mean labral height and slope differences between the 2 arm positions were 1.47 mm (standard deviation [SD], 0.75 mm; range, 0.6 mm to 3.5 mm; P < .001) and 6.91° (SD, 3.4°; range, 2.2° to 11.2°; P < .001), respectively. Medial overhang on the glenoid rim was 81% positive with the arm at internal rotation whereas medial overhang was 86% negative with the arm at external rotation (P < .001). On MR arthrography, internal rotation of shoulder showed the loss of the capsulolabral buttress in all patients. Conclusions: On MR arthrography, the arthroscopically repaired capsulolabral buttress was affected by rotation of the arm after Bankart repair. Internal rotation of the arm significantly decreased our ability to see the repaired capsulolabral buttress on MR arthrography. Level of Evidence: Level III, diagnostic study of nonconsecutive patients.